Is it possible to use two installations of Windows 10 on the same machine at the same time?
I have 3 real drives. One SSD, two classic hard drives. Windows 10 is currently installed on the SSD.
You can use multiple copies of Windows 10 in what's known as a Multi-Boot configuration. Often you'll hear of this as "Dual-booting", because most commonly only two different OSs are in question.
How To Geek has a nice tutorial about setting up dual boot with multiple copies of Windows, and a good explanation of dual-booting in general.
Legally, you need a licence for EACH Windows install you make. So if you want to install Windows 10 twice, you'll need to own two licenses for it, even if they're only running one at a time, on the same computer.
Similar has been discussed previously here on on SU:
Yeah, no you don't need 2 licences for a single machine since the installed devices are EXACTLY the same. Suggesting otherwise is pure greed and stupidity. Since even Microsoft can't tell, and even they would help you install it on a 2nd drive should you have trouble. The Eula specifically says a SINGLE machine Single instance. This is a single machine and you can only run 1 instance at a time. A 2nd win 10 on your machine is very wise, should your first drive fail, becomes corrupted, or virus and malware can be removed from your main win 10 install far easier using a 2nd. In regards to VM that is very specific in regards to requiring more then 1 VM to require more licences. Actually if your running Windows 10 and you want to run a VM on that machine, requires an additional license(s). I will admit MS does not make it easy to do so. Using cloning software is by far the easiest, because no matter how you partition the 2nd drive, it won't start win 10 installation. There's your vague part lol. But going by the EULA they have not said you can't have 2 installations using the same product ID. I think they would need to be very point blank about it as they have done with VM.
